Introduction: Osteosarcoma is one of the most common primary malignant tumors of the bone in which malignant mesenchymal cells have the capability of producing osteoid or immature bone. Osteosarcoma of the craniofacial bones accounts for 6% to 10% of all the cases and usually occurs in patients older than 20 years of age. As to morphologic and clinical aspects, osteosarcoma can be divided into several subgroups. Central low-grade osteosarcoma is a rare variant of osteosarcoma with minimal cellular anaplasticity.Case Report: The patient was an 18 year old girl who presented with a firm, painless, dome-shaped swelling with buccal and lingual extension of the symphysal region which was misdiagnosed as benign fibro-osseous lesions in two previous recurrences. In the third recurrence, the diagnosis of low-grade osteosarcoma with the foci of high grade transformation was finalized. Because low-grade osteosarcoma of the jaws appears histologically unremarkable, definite diagnosis of this neoplasm requires the study of numerous microscopic sections and correlation of the histological features, patient's history, and clinical and radiographic findings. In this study, the previous misdiagnosis, final diagnosis and treatment of this case have been discussed.Key words: Low-grade, Osteosarcoma, Mandibular symphysis, Fibro-osseous lesion